Thoth was the god of writing and wisdom. He invented the hieroglyphs (called "god’s words" by the Egyptians) and the languages and performed several tasks which have to do with writing.
Well known is his presence in the Hall of Justice, where the judgement of the dead took place. Thoth, standing near the scales on which the heart of the deceased was weighed against the feather of truth (symbol of the goddess Maat), wrote down the outcome of the investigation. Many copies of the Book of the Dead depict this moment (vignette of spell 125).
His task was also to determine the fate of a child (including the number of years it would live), which was done at the moment of birth. Similarly Thoth wrote down the names of the king on the leaves of a special tree. As inventor of languages Thoth also was an interpreter.
Thoth also differentiated the years, seasons and months, as the lord of time; since these were measured by observing the moon, Thoth also was a moon god. As such he controlled the course of the stars as well as the giving of offerings (which was related to the calendar), therefore he also was the leader of rituals.
Thoth could be portrayed as a man with the head of an ibis (very rarely the head of a man), entirely as an ibis or as a baboon. Sometimes the full moon and the crescent were added on his head. When depicted as a man he often had the palette of a scribe and a pen in his hands.
Thoth was venerated all over Egypt; cemeteries where thousands of ibises were buried attest this. But his most important cult centre was Khemenu (modern Ashmunein), also known as Hermopolis because Thoth was associated with the god Hermes in Ptolemaic times.